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The Issue

Mammography has been a key public health tool for decades. In 2000, however, Danish researchers asserted that major mammography studies of previous years are of questionable quality. They concluded that no reliable evidence has demonstrated that mammograms reduce breast cancer mortality.

The Expert

Kathy Helzlsouer, MD, MHS ’88, professor, Epidemiology and Oncology 

The Answers

Should women stop getting regular mammograms?
No. I think mammograms are beneficial. But we’re not quite as certain as before—and that’s not good enough. We need better tests for early diagnosis.
Are there risks to having mammograms?
There is minimal risk from radiation exposure—but any risk from that is exceeded by the potential benefits. There is a risk of a false-positive test, with all the associated anxieties and further evaluation that come with that, including possibly biopsies. Sometimes a cancer may be missed.  This could falsely reassure a woman. 

Why are there false positives?
A mammogram is a screening test to pick up an abnormality. To determine if cancer is present or not, a sample of tissue is needed. Mammograms have a lot more false positives in younger women. For women in their late 30s, false positives may be as high as 25 percent. They shouldn’t jump to the conclusion [that] this is cancer. Age is the biggest risk factor for cancer. The younger a woman is, the less common breast cancer is.

What should women age 40 do?
The U.S. Preventive Services Task Force recommends mammograms every 1 to 2 years for women over 40. These women should also find out what other factors might affect their risk, including a family history of breast cancer, early age of menstrual onset, birth of a first child after age 30, and a previous breast biopsy that showed atypical cells. Women at high risk will want to speak to their health care provider about when they should start mammography screening and how often. Tamoxifen may be used to lower the risk for these women. Avoiding hormone replacement therapy and maintaining a proper weight may also help to lower their risk. 

And women 50 and older?
There is stronger evidence that mammograms benefit women 50 and older. The test performs better because breast tissue becomes less dense with age, and abnormalities are easier to see on the X-ray.  Another reason is that breast cancer is more common as women age, so that the predictive value—the likelihood that an abnormal test means cancer is higher for older women.


An estimated 211,300 new cases of invasive breast cancer are expected to occur among U.S. women this year. It is the most frequently diagnosed non-skin cancer in women and the second leading cause of cancer deaths in women (after lung cancer). Health experts predict 39,800 breast cancer deaths among U.S. women this year. —American Cancer Society


U.S. Preventive Services Task Force   
Centers for Disease Control and Prevention     
American Cancer Society